2 * rsa.c: implementation of RSA with PKCS#1 padding
5 * This file is Free Software. It was originally written for secnet.
7 * Copyright 1995-2003 Stephen Early
8 * Copyright 2002-2014 Ian Jackson
9 * Copyright 2001 Simon Tatham
10 * Copyright 2013 Mark Wooding
12 * You may redistribute secnet as a whole and/or modify it under the
13 * terms of the GNU General Public License as published by the Free
14 * Software Foundation; either version 3, or (at your option) any
17 * You may redistribute this file and/or modify it under the terms of
18 * the GNU General Public License as published by the Free Software
19 * Foundation; either version 2, or (at your option) any later
22 * This software is distributed in the hope that it will be useful,
23 * but WITHOUT ANY WARRANTY; without even the implied warranty of
24 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
25 * GNU General Public License for more details.
27 * You should have received a copy of the GNU General Public License
28 * along with this software; if not, see
29 * https://www.gnu.org/licenses/gpl.html.
38 #include "unaligned.h"
40 #define AUTHFILE_ID_STRING "SSH PRIVATE KEY FILE FORMAT 1.1\n"
42 #define mpp(s,n) do { char *p = mpz_get_str(NULL,16,n); printf("%s 0x%sL\n", s, p); free(p); } while (0)
48 #define FREE(b) ({ free((b)); (b)=0; })
51 void (*verror)(struct load_ctx *l,
52 FILE *maybe_f, bool_t unsup,
53 const char *message, va_list args);
54 bool_t (*postreadcheck)(struct load_ctx *l, FILE *f);
65 static void verror_tryload(struct load_ctx *l,
66 FILE *maybe_f, bool_t unsup,
67 const char *message, va_list args)
69 int class=unsup ? M_DEBUG : M_ERR;
70 slilog_part(l->u.tryload.log,class,"%s: ",l->what);
71 vslilog(l->u.tryload.log,class,message,args);
74 static void verror_cfgfatal(struct load_ctx *l,
75 FILE *maybe_f, bool_t unsup,
76 const char *message, va_list args)
78 vcfgfatal_maybefile(maybe_f,*l->loc,l->what,message,args);
83 struct sigprivkey_if ops;
85 struct rsacommon common;
92 #define RSAPUB_BNS(each) \
93 each(0,e,"public exponent") \
96 #define RSAPUB_LOADCORE_PASSBN(ix,en,what) \
101 struct sigpubkey_if ops;
103 struct rsacommon common;
107 /* Sign data. NB data must be smaller than modulus */
109 #define RSA_MAX_MODBYTES 2048
110 /* The largest modulus I've seen is 15360 bits, which works out at 1920
111 * bytes. Using keys this big is quite implausible, but it doesn't cost us
112 * much to support them.
115 static const char *hexchars="0123456789abcdef";
117 static void rsa_sethash(struct rsacommon *c, struct hash_if *hash,
118 const struct hash_if **in_ops)
121 c->hashbuf=safe_malloc(hash->hlen, "generate_msg");
124 static void rsa_pub_sethash(void *sst, struct hash_if *hash)
126 struct rsapub *st=sst;
127 rsa_sethash(&st->common, hash, &st->ops.hash);
129 static void rsa_priv_sethash(void *sst, struct hash_if *hash)
131 struct rsapriv *st=sst;
132 rsa_sethash(&st->common, hash, &st->ops.hash);
134 static void rsacommon_dispose(struct rsacommon *c)
139 static void emsa_pkcs1(MP_INT *n, MP_INT *m,
140 const uint8_t *data, int32_t datalen)
142 char buff[2*RSA_MAX_MODBYTES + 1];
145 /* RSA PKCS#1 v1.5 signature padding:
147 * <------------ msize hex digits ---------->
149 * 00 01 ff ff .... ff ff 00 vv vv vv .... vv
153 * = datalen*2 hex digits
155 * NB that according to PKCS#1 v1.5 we're supposed to include a
156 * hash function OID in the data. We don't do that (because we
157 * don't have the hash function OID to hand here), thus violating
158 * the spec in a way that affects interop but not security.
163 msize=mpz_sizeinbase(n, 16);
165 if (datalen*2+6>=msize) {
166 fatal("rsa: message too big");
171 for (i=0; i<datalen; i++) {
172 buff[msize+(-datalen+i)*2]=hexchars[(data[i]&0xf0)>>4];
173 buff[msize+(-datalen+i)*2+1]=hexchars[data[i]&0xf];
176 buff[msize-datalen*2-2]= '0';
177 buff[msize-datalen*2-1]= '0';
179 for (i=4; i<msize-datalen*2-2; i++)
184 mpz_set_str(m, buff, 16);
187 static bool_t rsa_sign(void *sst, uint8_t *data, int32_t datalen,
188 struct buffer_if *msg)
190 struct rsapriv *st=sst;
191 MP_INT a, b, u, v, tmp, tmp2;
192 string_t signature = 0;
198 hash_hash(st->ops.hash,data,datalen,st->common.hashbuf);
199 /* Construct the message representative. */
200 emsa_pkcs1(&st->n, &a, st->common.hashbuf, st->ops.hash->hlen);
203 * Produce an RSA signature (a^d mod n) using the Chinese
204 * Remainder Theorem. We compute:
206 * u = a^dp mod p (== a^d mod p, since dp == d mod (p-1))
207 * v = a^dq mod q (== a^d mod q, similarly)
209 * We also know w == iqmp * q, which has the property that w ==
210 * 0 mod q and w == 1 mod p. So (1-w) has the reverse property
211 * (congruent to 0 mod p and to 1 mod q). Hence we now compute
213 * b = w * u + (1-w) * v
216 * so that b is congruent to a^d both mod p and mod q. Hence b,
217 * reduced mod n, is the required signature.
224 mpz_powm_sec(&u, &a, &st->dp, &st->p);
225 mpz_powm_sec(&v, &a, &st->dq, &st->q);
226 mpz_sub(&tmp, &u, &v);
227 mpz_mul(&tmp2, &tmp, &st->w);
228 mpz_add(&tmp, &tmp2, &v);
229 mpz_mod(&b, &tmp, &st->n);
236 signature=write_mpstring(&b);
238 uint8_t *op = buf_append(msg,2);
239 if (!op) { ok=False; goto out; }
240 size_t l = strlen(signature);
243 op = buf_append(msg,l);
244 if (!op) { ok=False; goto out; }
245 memcpy(op, signature, l);
256 static bool_t rsa_sig_unpick(void *sst, struct buffer_if *msg,
257 struct alg_msg_data *sig)
259 uint8_t *lp = buf_unprepend(msg, 2);
260 if (!lp) return False;
261 sig->len = get_uint16(lp);
262 sig->start = buf_unprepend(msg, sig->len);
263 if (!sig->start) return False;
265 /* In `rsa_sig_check' below, we assume that we can write a nul
266 * terminator following the signature. Make sure there's enough space.
268 if (msg->start >= msg->base + msg->alloclen)
274 static sig_checksig_fn rsa_sig_check;
275 static bool_t rsa_sig_check(void *sst, uint8_t *data, int32_t datalen,
276 const struct alg_msg_data *sig)
278 struct rsapub *st=sst;
286 hash_hash(st->ops.hash,data,datalen,st->common.hashbuf);
287 emsa_pkcs1(&st->n, &a, st->common.hashbuf, st->ops.hash->hlen);
289 /* Terminate signature with a '0' - already checked that this will fit */
290 int save = sig->start[sig->len];
291 sig->start[sig->len] = 0;
292 mpz_set_str(&b, sig->start, 16);
293 sig->start[sig->len] = save;
295 mpz_powm(&c, &b, &st->e, &st->n);
297 ok=(mpz_cmp(&a, &c)==0);
306 static void rsapub_dispose(void *sst) {
307 struct rsapub *st=sst;
311 rsacommon_dispose(&st->common);
315 #define RSAPUB_LOADCORE_DEFBN(ix,en,what) \
316 const char *en##s, struct cloc en##_loc,
318 static struct rsapub *rsa_loadpub_core(RSAPUB_BNS(RSAPUB_LOADCORE_DEFBN)
319 struct cloc overall_loc)
324 st->cl.description="rsapub";
325 st->cl.type=CL_SIGPUBKEY;
327 st->cl.interface=&st->ops;
329 st->ops.sethash=rsa_pub_sethash;
330 st->common.hashbuf=NULL;
331 st->ops.unpick=rsa_sig_unpick;
332 st->ops.check=rsa_sig_check;
334 st->ops.dispose=rsapub_dispose;
337 #define RSAPUB_LOADCORE_GETBN(ix,en,what) \
338 if (mpz_init_set_str(&st->en,en##s,10)!=0) { \
339 cfgfatal(en##_loc,"rsa-public", what " \"%s\" is not a " \
340 "decimal number string\n",en##s); \
342 if (mpz_sizeinbase(&st->en, 256) > RSA_MAX_MODBYTES) { \
343 cfgfatal(en##_loc, "rsa-public", "implausibly large " what "\n"); \
346 RSAPUB_BNS(RSAPUB_LOADCORE_GETBN)
351 static list_t *rsapub_apply(closure_t *self, struct cloc loc, dict_t *context,
355 #define RSAPUB_APPLY_GETBN(ix,en,what) \
358 en##i=list_elem(args,ix); \
360 cfgfatal(loc,"rsa-public", \
361 "you must provide an encryption key\n"); \
362 struct cloc en##_loc=en##i->loc; \
363 if (en##i->type!=t_string) \
364 cfgfatal(en##_loc,"rsa-public", \
365 "first argument must be a string\n"); \
366 en##s=en##i->data.string;
368 RSAPUB_BNS(RSAPUB_APPLY_GETBN)
370 struct rsapub *st=rsa_loadpub_core(RSAPUB_BNS(RSAPUB_LOADCORE_PASSBN)
373 return new_closure(&st->cl);
376 static void load_error(struct load_ctx *l, FILE *maybe_f,
377 bool_t unsup, const char *fmt, ...)
381 l->verror(l,maybe_f,unsup,fmt,al);
385 #define LDFATAL(...) ({ load_error(l,0,0,__VA_ARGS__); goto error_out; })
386 #define LDUNSUP(...) ({ load_error(l,0,1,__VA_ARGS__); goto error_out; })
387 #define LDFATAL_FILE(...) ({ load_error(l,f,0,__VA_ARGS__); goto error_out; })
388 #define LDUNSUP_FILE(...) ({ load_error(l,f,1,__VA_ARGS__); goto error_out; })
389 #define KEYFILE_GET(is) ({ \
390 uint##is##_t keyfile_get_tmp=keyfile_get_##is(l,f); \
391 if (!l->postreadcheck(l,f)) goto error_out; \
395 static uint32_t keyfile_get_32(struct load_ctx *l, FILE *f)
405 static uint16_t keyfile_get_16(struct load_ctx *l, FILE *f)
413 static void rsapriv_dispose(void *sst)
415 struct rsapriv *st=sst;
417 mpz_clear(&st->p); mpz_clear(&st->dp);
418 mpz_clear(&st->q); mpz_clear(&st->dq);
420 rsacommon_dispose(&st->common);
424 static struct rsapriv *rsa_loadpriv_core(struct load_ctx *l,
425 FILE *f, struct cloc loc,
426 bool_t do_validity_check)
428 struct rsapriv *st=0;
432 MP_INT e,d,iqmp,tmp,tmp2,tmp3;
443 st->cl.description="rsapriv";
444 st->cl.type=CL_SIGPRIVKEY;
446 st->cl.interface=&st->ops;
448 st->ops.sethash=rsa_priv_sethash;
449 st->common.hashbuf=NULL;
450 st->ops.sign=rsa_sign;
452 st->ops.dispose=rsapriv_dispose;
462 assert(just_check_config);
466 /* Check that the ID string is correct */
467 length=strlen(AUTHFILE_ID_STRING)+1;
468 b=safe_malloc(length,"rsapriv_apply");
469 if (fread(b,length,1,f)!=1 || memcmp(b,AUTHFILE_ID_STRING,length)!=0) {
470 LDUNSUP_FILE("failed to read magic ID"
471 " string from SSH1 private keyfile\n");
475 cipher_type=fgetc(f);
476 KEYFILE_GET(32); /* "Reserved data" */
477 if (cipher_type != 0) {
478 LDUNSUP("we don't support encrypted keyfiles\n");
481 /* Read the public key */
482 KEYFILE_GET(32); /* Not sure what this is */
483 length=(KEYFILE_GET(16)+7)/8;
484 if (length>RSA_MAX_MODBYTES) {
485 LDFATAL("implausible length %ld for modulus\n",
488 b=safe_malloc(length,"rsapriv_apply");
489 if (fread(b,length,1,f) != 1) {
490 LDFATAL_FILE("error reading modulus\n");
492 read_mpbin(&st->n,b,length);
494 length=(KEYFILE_GET(16)+7)/8;
495 if (length>RSA_MAX_MODBYTES) {
496 LDFATAL("implausible length %ld for e\n",length);
498 b=safe_malloc(length,"rsapriv_apply");
499 if (fread(b,length,1,f)!=1) {
500 LDFATAL_FILE("error reading e\n");
502 read_mpbin(&e,b,length);
505 length=KEYFILE_GET(32);
507 LDFATAL("implausibly long (%ld) key comment\n",
510 c=safe_malloc(length+1,"rsapriv_apply");
511 if (fread(c,length,1,f)!=1) {
512 LDFATAL_FILE("error reading key comment\n");
516 /* Check that the next two pairs of characters are identical - the
517 keyfile is not encrypted, so they should be */
519 if (KEYFILE_GET(16) != KEYFILE_GET(16)) {
520 LDFATAL("corrupt keyfile\n");
524 length=(KEYFILE_GET(16)+7)/8;
525 if (length>RSA_MAX_MODBYTES) {
526 LDFATAL("implausibly long (%ld) decryption key\n",
529 b=safe_malloc(length,"rsapriv_apply");
530 if (fread(b,length,1,f)!=1) {
531 LDFATAL_FILE("error reading decryption key\n");
533 read_mpbin(&d,b,length);
535 /* Read iqmp (inverse of q mod p) */
536 length=(KEYFILE_GET(16)+7)/8;
537 if (length>RSA_MAX_MODBYTES) {
538 LDFATAL("implausibly long (%ld)"
539 " iqmp auxiliary value\n", length);
541 b=safe_malloc(length,"rsapriv_apply");
542 if (fread(b,length,1,f)!=1) {
543 LDFATAL_FILE("error reading decryption key\n");
545 read_mpbin(&iqmp,b,length);
547 /* Read q (the smaller of the two primes) */
548 length=(KEYFILE_GET(16)+7)/8;
549 if (length>RSA_MAX_MODBYTES) {
550 LDFATAL("implausibly long (%ld) q value\n",
553 b=safe_malloc(length,"rsapriv_apply");
554 if (fread(b,length,1,f)!=1) {
555 LDFATAL_FILE("error reading q value\n");
557 read_mpbin(&st->q,b,length);
559 /* Read p (the larger of the two primes) */
560 length=(KEYFILE_GET(16)+7)/8;
561 if (length>RSA_MAX_MODBYTES) {
562 LDFATAL("implausibly long (%ld) p value\n",
565 b=safe_malloc(length,"rsapriv_apply");
566 if (fread(b,length,1,f)!=1) {
567 LDFATAL_FILE("error reading p value\n");
569 read_mpbin(&st->p,b,length);
573 fatal_perror("rsa-private (%s:%d): ferror",loc.file,loc.line);
577 * Now verify the validity of the key, and set up the auxiliary
578 * values for fast CRT signing.
581 if (do_validity_check) {
582 /* Verify that p*q is equal to n. */
583 mpz_mul(&tmp, &st->p, &st->q);
584 if (mpz_cmp(&tmp, &st->n) != 0)
588 * Verify that d*e is congruent to 1 mod (p-1), and mod
589 * (q-1). This is equivalent to it being congruent to 1 mod
590 * lambda(n) = lcm(p-1,q-1). The usual `textbook' condition,
591 * that d e == 1 (mod (p-1)(q-1)) is sufficient, but not
592 * actually necessary.
594 mpz_mul(&tmp, &d, &e);
595 mpz_sub_ui(&tmp2, &st->p, 1);
596 mpz_mod(&tmp3, &tmp, &tmp2);
597 if (mpz_cmp_si(&tmp3, 1) != 0)
599 mpz_sub_ui(&tmp2, &st->q, 1);
600 mpz_mod(&tmp3, &tmp, &tmp2);
601 if (mpz_cmp_si(&tmp3, 1) != 0)
604 /* Verify that q*iqmp is congruent to 1 mod p. */
605 mpz_mul(&tmp, &st->q, &iqmp);
606 mpz_mod(&tmp2, &tmp, &st->p);
607 if (mpz_cmp_si(&tmp2, 1) != 0)
610 /* Now we know the key is valid (or we don't care). */
614 * Now we compute auxiliary values dp, dq and w to allow us
615 * to use the CRT optimisation when signing.
617 * dp == d mod (p-1) so that a^dp == a^d mod p, for all a
618 * dq == d mod (q-1) similarly mod q
619 * w == iqmp * q so that w == 0 mod q, and w == 1 mod p
621 mpz_sub_ui(&tmp, &st->p, 1);
622 mpz_mod(&st->dp, &d, &tmp);
623 mpz_sub_ui(&tmp, &st->q, 1);
624 mpz_mod(&st->dq, &d, &tmp);
625 mpz_mul(&st->w, &iqmp, &st->q);
629 LDFATAL("file does not contain a "
648 if (st) rsapriv_dispose(st);
653 static bool_t postreadcheck_tryload(struct load_ctx *l, FILE *f)
656 if (feof(f)) { load_error(l,0,0,"eof mid-integer"); return False; }
660 bool_t rsa1_loadpriv(const struct sigscheme_info *algo,
661 struct buffer_if *privkeydata,
662 struct sigprivkey_if **sigpriv_r,
663 struct log_if *log, struct cloc loc)
666 struct rsapriv *st=0;
668 f=fmemopen(privkeydata->start,privkeydata->size,"r");
670 slilog(log,M_ERR,"failed to fmemopen private key file\n");
674 struct load_ctx l[1];
675 l->what="rsa1priv load";
676 l->verror=verror_tryload;
677 l->postreadcheck=postreadcheck_tryload;
679 l->u.tryload.log=log;
681 st=rsa_loadpriv_core(l,f,loc,False);
682 if (!st) goto error_out;
686 if (st) { free(st); st=0; }
689 if (!st) return False;
694 static bool_t postreadcheck_apply(struct load_ctx *l, FILE *f)
696 cfgfile_postreadcheck(*l->loc,f);
700 static list_t *rsapriv_apply(closure_t *self, struct cloc loc, dict_t *context,
707 struct load_ctx l[1];
709 l->what="rsa-private";
710 l->verror=verror_cfgfatal;
711 l->postreadcheck=postreadcheck_apply;
714 /* Argument is filename pointing to SSH1 private key file */
717 if (i->type!=t_string) {
718 cfgfatal(i->loc,"rsa-private","first argument must be a string\n");
720 filename=i->data.string;
722 filename=NULL; /* Make compiler happy */
723 cfgfatal(i->loc,"rsa-private","you must provide a filename\n");
726 f=fopen(filename,"rb");
728 if (just_check_config) {
729 Message(M_WARNING,"rsa-private (%s:%d): cannot open keyfile "
730 "\"%s\"; assuming it's valid while we check the "
731 "rest of the configuration\n",loc.file,loc.line,filename);
733 fatal_perror("rsa-private (%s:%d): cannot open file \"%s\"",
734 loc.file,loc.line,filename);
738 bool_t do_validity_check=True;
740 if (i && i->type==t_bool && i->data.bool==False) {
741 Message(M_INFO,"rsa-private (%s:%d): skipping RSA key validity "
742 "check\n",loc.file,loc.line);
743 do_validity_check=False;
746 st=rsa_loadpriv_core(l,f,loc,do_validity_check);
748 return new_closure(&st->cl);
751 void rsa_module(dict_t *dict)
753 add_closure(dict,"rsa-private",rsapriv_apply);
754 add_closure(dict,"rsa-public",rsapub_apply);